Today, new radio access technologies are being specified and subsequently implemented by operators of cellular telecommunications systems. Consequently it has become more and more common that one operator of a radio systems network has several radio access technologies being deployed concurrently in the same geographical area.
At the same time, mobile terminals are becoming more and more sophisticated often comprising capabilities for communicating over more than one type of radio access. Such evolution will impose a requirement to be able to use multi-access capabilities in an optimal way so that operator can make best usage of the deployed radio technologies. One of the most decisive parameters for optimizing the usage is the currently used capacity in different radio access technologies (RATs).
Examples of deployed technologies include GSM with sub-standards such as the General Packet Radio Services (GPRS) and the Enhanced Data rates for GSM Evolution (EDGE). There is also WCDMA, with the sub-standard High-Speed Downlink Packet Access (HSDPA) has been introduced. Other standards are CDMA and Long Term Evolution (LTE).
As stated above, a multitude of standards may exist overlapping within an area served by an operator and the operator of such a combined network of different standards is faced with the problem of having to manage the resources within the combined network in a way that both maximizes the use of the combined resources and maximizes the service provided to each mobile user within the combined network.
Traditionally, wireless communication systems for special usage like police, fire brigade and civil defense are deployed as dedicated systems (e.g. TETRA technology). Such solutions are expensive for the country administration. Therefore, more and more requirements are put onto commercial systems to be able to adequately accommodate high priority traffic when needed.
In a single access environment it means that “ordinary” traffic is down prioritized at service request. The same approach can be applied in a multi-access environment but there is still a risk of having congestion situation on the random access channel of the respective RAT.
Alternatively, some “ordinary” mobile stations can be refused to make location update in a location area belonging to a certain access or even refused a service upon invocation so that it can be exclusively used for priority traffic. However, both those methods are slow and with worse performance.
Hence, there exists a need for a method and a system that is able to guarantee radio access to prioritized subscribers in case of an emergency, which is inexpensive to implement, which is reliable and which provides high performance.